Knee Cartilage Replacement Therapy - Autologous Chondrocyte Implantation

Autologous Chondrocyte Implantation

The human body's own cartilage is still the best material for lining knee joints. This drives efforts to develop ways of using a person's own cells to grow, or re-grow cartilage tissue to replace missing or damaged cartilage. One cell-based replacement technique is called autologous chondrocyte implantation (ACI) or autologous chondrocyte transplantation (ACT).

A review evaluating autologous chondrocyte implantation was published in 2010. The conclusions are that it is an effective treatment for full thickness chondral defects. The evidence does not suggest ACI is superior to other treatments.

One ACI treatment, called Carticel, is designated for young, healthy patients with medium to large sized damage to cartilage and is not applicable to osteoarthritis patients. The patient’s chondrocytes are removed arthroscopically from a non load-bearing area from either the intercondylar notch or the superior ridge of the medial or lateral femoral condyles. 10,000 cells are harvested and grown in vitro for approximately six weeks until the population reaches 10-12 million cells. Then these cells are injected into the patient. These cells are held in place by a small piece of soft tissue from the tibia, called a periosteal flap, which is sutured over the area to serve as a watertight lid. The implanted chondrocytes then divide and integrate with surrounding tissue and potentially generate hyaline-like cartilage. The cost of the treatment ranges from ($USD) 20,000-35,000. A second generation technique, called Carticel II uses a "fleece matrix" implanted with chondrocyte cells that is arthroscopically inserted into the joint. This procedure is known as matrix autologous chondrocyte implantation or (MACI) and is available in Germany, UK, and Australia.

A variation on the Carticel technique, called matrix-associated autologous chondrocyte transplantation (MACT), grows the patient's cells in a 3D matrix of resorbable tissue which is implanted via an open or arthroscopic procedure. It appears to be a simpler technique and resolves some of the issues of using Carticel under a periosteal patch.

Another ACI technique, using "chrondospheres", uses only chrondrocytes and no matrix material. The cells grow in self-organized spheroid matrices which are implanted via injected fluid or inserted tissue matrix.